Here are a few commands for running the Windows Update Agent from a command line:

Force detection of updates:
wuauclt /detectnow

Force reporting status to an Windows Update Server:
wuauclt /r /ReportNow

Stop and start the automatic updates service:
net stop wuauserv
net start wuauserv

To help troubleshooting here’s where the log is normally.

Some more documentation on Microsoft’s Technet site.